Swift - Convert a short format string of a date to long format using date formatter

Question

I have a string that looks like this: "2021-08-05"

I would like to convert it into a date so that I can display it as "5th August 2021"

My code below just returns as nil and I don't understand why. Any help would be appreciated.

Code:

func stringToDate(dateString: String){
  let formatter = DateFormatter()

  formatter.locale = Locale(identifier: "en_US_POSIX")
  formatter.dateFormat = "yyyy-MM-dd"
  formatter.dateStyle = .long
        
  let newDate = formatter.date(from: dateString)

  print("formatter: \(newDate)")
}

I call the function as an action for a button (SwiftUI), so when the button is clicked the date should show.

Button("Go"){
 stringToDate(dateString: "2021-08-05")
}

Answer 1

Removing the dateStyle line fixes it, and an actual date is printed.

Code:

func stringToDate(dateString: String){
    let formatter = DateFormatter()
    formatter.locale = Locale(identifier: "en_US_POSIX")
    formatter.dateFormat = "yyyy-MM-dd"

    let newDate = formatter.date(from: dateString)
    print("formatter: \(newDate)")
}

// Prints: formatter: Optional(2021-08-04 23:00:00 +0000)

To do the whole conversion, the following function will work:

func convertDate(from original: String) -> String? {
    let formatter = DateFormatter()
    formatter.locale = Locale(identifier: "en_US_POSIX")
    formatter.dateFormat = "yyyy-MM-dd"
    guard let date = formatter.date(from: original) else { return nil }
    formatter.dateStyle = .long
    let string = formatter.string(from: date)
    return string
}

// Prints: Optional("August 5, 2021")

Of course, this may be printed slightly different due to my location & language

The following line of code can only be run after getting a Date otherwise you are 'overwriting' the dateFormat:

formatter.dateStyle = .long